1. Technical Field
This invention relates generally to covers for truck beds for protecting the cargo and preventing loose cargo from being blown out during transport. More specifically, this invention relates to flexible tarp covers that can be unrolled to cover the truck bed and rerolled to one side for storage.
2. Background Art
Truck bed covers are especially useful, and are sometimes required, for transport of farm produce and bulk materials that tend to blow out of the bed when the truck is at highway speeds.
Some designs feature a flexible cover that is drawn or unrolled along a track. Heider et al. (U.S. Pat. Nos. 4,529,098 and 4,518,193) places a track means along the upper edge of a box end wall, and uses a motor to rotate a shaft back and forth along the track to wind and unwind a sheet member. Killion (U.S. Pat. No. 4,023,857) moves a winding member back and forth across the truck bed on support arms moving on a generally horizontal track. Biancale (U.S. Pat. No. 4,281,872) discloses an accordion-folded tarpaulin that is drawn in window-drape fashion across a truck bed on support rods by a cable system.
Some designs use a pivot arm to move a flexible cover. Fredin (U.S. Pat. No. 4,225,175) uses a piston to pivot two arms that carry a shaft and a tarp back and forth across a transport box. In Fredin, a pull-belt winds and unwinds onto the shaft in opposite directions to the tarp and acts as a biasing means to rotate the shaft to roll and unroll the tarp. Petretti (U.S. Pat. No. 4,030,780) uses a motor or crank to turn a pivot rod located underneath a truck bed, and the pivot rod swings two arms that carry a roller rod. Two cables, oppositely wound around the roller rod, bias the roller rod to roll and unroll a canvas cover. Alternatively, Petretti discloses a pivot rod and swing arm system in which a motor rotates a stationary roller to reel in and out the canvas cover, and a spring system to move the arms back to the rear of the truck to extend the cover over the truck bed. Richard (U.S. Pat. No. 4,050,734) discloses piston-operated arms which swing a take-up roller that has a spring bias for rotation to roll up a flexible top cover. Tsukamoto (U.S. Pat. No. 4,673,208) discloses two swing arms pivoted by hydraulic pistons operating in master-slave relationship and a roller that is rotatably held by the two arms. The Tsukamoto system has a chain and sprocket system trained over a stationary track and trained up to a sprocket on the roller to rotate the roller to roll and unroll the cover sheet. The Tsukamoto system also has imperforate plates for closing up the gaps between the cover sheet and the truck bed walls.